1. Technical Field
The present disclosure relates to surgical fastener applying apparatus. More particularly, the present disclosure relates to a tool assembly for use with a surgical fastener applying apparatus, and methods of manufacturing the same, to apply a plurality of surgical fasteners to tissue with varying compressive forces.
2. Background of the Related Art
Many varieties of surgical fastener applying apparatus are known in the art, some of which are specifically adapted for use in various surgical procedures including, but not limited to, end-to-end anastomosis, circular end-to-end anastomosis, open gastrointestinal anastomosis, endoscopic gastrointestinal anastomosis, and transverse anastomosis. Suitable examples of apparatus which may be used during the course of these procedures can be seen in U.S. Pat. Nos. 5,915,616; 6,202,914; 5,865,361; and 5,964,394.
In general, a surgical fastener applying apparatus will include an anvil that is approximated relative to a surgical fastener cartridge during use. The anvil includes depressions that are aligned with, and/or are in registration with, slots defined in the surgical fastener cartridge, through which the surgical fasteners will emerge. To effectuate formation, the surgical fasteners emerge from the surgical fastener cartridge and are driven against the anvil. The surgical fastener cartridge typically has one or more rows of surgical fasteners that are disposed laterally outward of a slot that is configured to accommodate a knife, or other such cutting element, such that tissue can be simultaneously severed and joined together at a cut-line. Depending upon the particular surgical fastener applying apparatus, the rows of fasteners may be arranged in a linear, non-linear, e.g. circular, semi-circular, or other configuration.
Various types of surgical fasteners are well known in the art including, but not limited to, unitary fasteners and two-part fasteners. Unitary fasteners generally include a pair of legs that are adapted to penetrate tissue and connected by a backspan from which they extend. In use, subsequent to formation, certain types of unitary fasteners have a “B” shaped configuration. Typically, the two-part fastener includes legs that are barbed and connected by a backspan. The legs are engaged and locked into a separate retainer piece that is usually located in the anvil. In use, the two-part fastener is pressed into the tissue so that the barbs penetrate the tissue and emerge from the other side where they are then locked into the retainer piece. The retainers prevent the two-part fastener from dislodging from the tissue. The two-part fasteners are not intended to be unlocked or removable. For this reason, they are generally made of a bioabsorbable material.
A common concern in each of the procedures mentioned above is hemostasis, or the rate at which bleeding of the target tissue is stopped. It is commonly known that by increasing the amount of pressure applied to a wound, the flow of blood can be limited, thereby decreasing the time necessary to achieve hemostasis. To this end, conventional surgical fastener applying apparatus generally apply two or more rows of fasteners about the cut-line to compress the surrounding tissue in an effort to stop any bleeding and to join the cut tissue together. Each of the surgical fasteners will generally apply a compressive force to the tissue that is sufficient to effectuate hemostasis. However, applying too much pressure can result in a needless reduction in blood flow to the tissue surrounding the cut-line, resulting in an elevated level of necrosis, a slower rate of healing, and/or a greater recovery period.
Consequently, it would be advantageous to provide a surgical fastener applying apparatus capable of limiting the flow of blood in the tissue immediately adjacent the cut-line to effectuate hemostasis and wound closure, while maximizing blood flow in the surrounding tissue to facilitate healing. Additionally, when tissue is clamped and compressed between the anvil and cartridge, some of the fluid retained within the tissue is squeezed out, which results in greater compression at the portions of the cartridge and the anvil adjacent the cut-line when compared to the lateral edges. It may also be desirable to cut and fasten across tissue that varies in thickness. It would therefore be advantageous to provide fasteners and surgical fastener applying apparatus that are better adapted to apply variable compressive forces to tissue in the interests of addressing these concerns.